Tools for the analysis of dose optimization: III. Pointwise sensitivity and perturbation analysis.
The major challenge in intensity-modulated radiotherapy planning is to find the right balance between tumor control and normal tissue sparing. The most desirable solution is never physically feasible, and a compromise has to be found. One possible way to approach this problem is constrained optimization. In this context, it is worthwhile to quantitatively predict the impact of adjustments of the constraints on the optimum dose distribution. This has been dealt with in regard to cost functions in a previous paper. The aim of the present paper is to introduce spatial resolution to this formalism. Our method reveals the active constraints in a target subvolume that was previously selected by the practitioner for its insufficient dose. This is useful if a multitude of constraints can be the cause of a cold spot. The response of the optimal dose distribution to an adjustment of constraints (perturbation) is predicted. We conclude with a clinical example.
Sobotta
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Abt. Medizinische Physik, Radiologische Uniklinik, Universität Tübingen, 72076 Tübingen, Germany. benjamin.sobotta@med.uni-tuebingen.de
Söhn
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Pütz
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Alber
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D000465:Algorithms; D006801:Humans; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012680:Sensitivity and Specificity